Northrop F-89J Scorpion

Last revised July 11, 2009

The F-89J (Model N-160) was the designation given to earlier F-89Ds that were modified in service to carry the
Douglas MB-1 Genie nuclear-tipped unguided air-to-air rocket.

Development of the Genie rocket was begun by Douglas Aircraft in 1955, with the Los Alamos National Laboratory
being given the responsibility for the nuclear warhead. The Genie rocket was unguided, relying on the power
of its nuclear warhead rather than on guidance to ensure a kill. The MB-1 Genie rocket was powered by a
36,600 pound thrust Thiokol TU-389 rocket motor. Launch weight was 822 pounds, and maximum velocity was
about Mach 3.3. There was a set of flick-out fin-tips which gave the Genie stability in flight and which
corrected for roll and gravity drop. The range of the Genie was about 6 miles, and the rocket was equipped
with a W25 nuclear warhead with a 1.5-kiloton yield. The lethal radius of the blast was estimated to be
about 1000 feet.

The F-89J was equipped to carry two Genies on launching rails that were mounted on the underwing pylons. On most F-89Js, the wingtip armament pods of the F-89D were removed and replaced by 600-gallon fuel tanks, although a few F-89Js still retained the standard F-89D wingtip pods. Later, the F-89J was further modified by adding two additional underwing pylons on each wing located inboard of the Genie pylon for Falcon air-to-air missiles. These four Falcons carried conventional high-explosive warheads. However, in practice these Falcons were rarely carried and the extra pylons were often removed.

The F-89J was equipped with the Hughes MG-12 fire control system, an upgraded and more advanced version of
the E-5 of the F-89D. This system made it possible for the crew to launch the Genie while in a nose-up,
climbing attitude, making it possible to attack bombers that were flying at a much higher altitude.
During an intercept, the Hughes fire-control system tracked the target, assigned the missile, commanded
the pilot to arm the nuclear warhead, fired the missile, pulled the interceptor into a tight turn to escape
the detonation, then triggered the nuclear warhead by remote control at the right moment.

The modified F-89J became known as "Weapons System 205G". Initial deliveries of the F-89J were made during November of 1956, with the 84th Fighter Interceptor Squadron at Hamilton AFB in California being the first receipient. This squadron began standing active alerts on January 1, 1957. Initially, the aircraft were armed with just one Genie rocket.

There were a total of 350 F-89Ds modified to F-89J standards. The planes were taken from the D-35 through D-75 production blocks. These modifications were carried out between March of 1956 and February of 1958.

The first production Genie rockets arrived in the field in May of 1957. Approximately 3150 Genies and their associated nuclear warheads were manufactured between 1956 and 1963. In 1962, the designation of the Genie was changed to AIR-2A.

The first live firing of a nuclear-tipped Genie took place on July 19, 1957, during a series of nuclear tests known as Operation PLUM BOB. On that day, F-89J serial number 53-2547 fired an MB-1 over the Yucca Flats Nuclear Test Site, and the warhead was detonated at an altitude of 15,000 feet by a signal from the ground. This shot, named JOHN, made the Scorpion the first interceptor in history to launch a nuclear weapon. In order to prove that the Genie could safely be used over populated areas in the US, several Air Force officers volunteered to stand on the ground directly underneath the detonation point. Following the test, these men were apparently unharmed, although I suppose that one might want to check and see what happened to them in later years.

The F-89J, with the two nuclear Genies and the four Falcons (plus 104 FFAR rockets when carrying the F-89D pods), was the most heavily-armed interceptor in the USAF inventory. However, the F-89J was destined for only a short service life, being replaced by the supersonic McDonnell F-101B Voodoo and the Convair F-106A Delta Dart starting in July of 1959.

The F-89Js were then transferred to the Air National Guard. By 1962, some nine ANG squadrons were equipped with nuclear-armed F-89Js. Air National Guard units stood numerous nuclear alerts. The F-89J remained in service with the 132nd FIS of the Maine ANG and the 134th FIS of the Iowa ANG until late 1968, when they were replaced by supersonic aircraft.

In 1963, ten F-89Js had their nose radars removed and were fitted with additional underwing fuel tanks and were used for testing of Nike missile defenses in Japan. These aircraft were redesignated DF-89J.

Sources:

United States Military Aircraft Since 1909, Gordon Swanborough
and Peter M. Bowers, Smithsonian, 1989.